Mössbauer and magnetic studies of BaVS3 and V5S8 doped with 57Fe

Iron can be easily introduced in BaVS₃ and V₅S₈. It is located at the vanadium sites and has been used as a probe to analyse by Mössbauer effect the magnetic properties of its surrounding matrix. The electronic state of iron in this matrix has also been studied. It was found that in BaVS₃, the iron is in a low spin Fe³⁺ configuration $\text{(S =}\text{1}\text{2}\text{)}$. In V₅S₈ at 4.2 K, the iron is in low spin Fe²⁺ configuration (S = 0). The rapid decrease of quadrupole splitting observed between 50 and 200 K is attributed to a thermally activated change in electronic structure. The high temperature configuration (above 200 K) seems to be neither pure low spin Fe³⁺ nor high spin Fe²⁺, but a mixture of configurations fluctuating at a rate which is faster than the characteristic time of Mössbauer measurements.     

ESR study of Mn2+ in sodium β″-alumina

ESR measurements are reported on Mn²⁺ diffused into sodium β″-alumina. The spin Hamiltonian parameters obtained are g₁₁ = 2.0000(2), $\text{g}{}_{\mathrm{?}}\text{= 2.0019(2)}$, A₁₁ = ?8.39(3) mT, $\text{A}{}_{\mathrm{?}}\text{= ?8.33(3)}\text{mT}$ and D = ?7.20(5) mT. The site position of the Mn²⁺ ions is discussed and compared to published results for Mn²⁺ in sodium β-alumina.     

Electronic structure calculation of Mn-doped GaAs

The molecular cluster model, within the framework of the self-consistent field multiple scattering Xα method, is applied to calculate the electronic structure of a Mn substitutional impurity in GaAs. The charge states Mn³⁺, with spin configurations S = 0 and 2, and Mn²⁺, with $\text{S}\text{=}\text{5}\text{2}$, were analysed. The theoretical results compare fairly well with the experimental data obtained from ESR and optical spectroscopic experiments.     

NMR spin lattice relaxation in dilute CuFe alloys with impurity interactions

Previous measurements by Wilkening and Hesse have shown, that the excess relaxation rate ΔT^-1₁ of the matrix nuclei in $\text{CuF}$e dilute alloys can be explained in terms of the LD-model with rapid spin diffusion. Measurements reported in this paper confirm the existence of an electric quadrupole diffusion barrier. It could be shown that the influence of the quadrupole barrier is coupled to large clusters within the alloy. The electron spin lattice relaxation time τ₁ behaves temperature independent in the range 30 K ? T ? 300 K. This can be understood if an effective correlation time τ is introduced, which results from a distrubution of temperature dependent times τ^cl(T) belonging to clusters of different size.     

Spin waves in an Invar alloy (Fe0.65Ni0.35)

The spin wave dispersion relation in an Invar alloy Fe_0.65Ni_0.35 has been measured at 4.2 K in the [111] direction by neutron inelastic scattering.Well defined magnon groups have been observed up to an energy transfer of about 80 meV. The spin wave dispersion is well described by ?ω=Dq²(1?βq²) with $\text{D=143}\text{meV}\text{A}\text{?}$ and $\text{β=0.12}\text{A}\text{?}{}^2$. The value of D is in accord with the value extrapolated from other neutron scattering results at higher contents of Ni and disagrees with spin wave resonance results.No trace of γ-iron type antiferromagnetic order could be detected at 4.2 K in this alloy by elastic neutron scattering measurements.     

SIMS,AES, work function and flash desorption measurements of the CO adsorption on NiCu alloy surfaces

The chemisorption of CO on Cu, Ni and CuNi alloy surfaces was examined by SIMS, work function measurements and desorption spectroscopy. Using a dynamic SIMS technique the M⁺, M⁺₂, MCO⁺ and M₂CO⁺ emission at different temperatures (100–400 K) was measured as a function of CO exposure. In agreement with the work function and desorption experiments an increase of M⁺ and MCO⁺ emission due to the CO adsorption on Cu was found only at low temperatures (100–190 K). On the Ni surface an increase of Ni⁺, NiCO⁺ and Ni₂CO⁺ was measured up to 400 K. The adsorption of CO on CuNi alloy surfaces — as derived from the work function measurements — can be described by the assumption of two different states of adsorbed carbon monoxide. They can be characterized by different binding energies and from sign and magnitude different work function changes. These states were interpreted as adsorption at Ni or Cu sites of the alloy surfaces, respectively. To a certain extent the SIMS results from the alloy surfaces are incompatible with the work function measurements and desorption spectroscopy and the SIMS studies on the pure metals. A Cu⁺ emission with comparable intensity to the Ni⁺ emission was found for alloys with bulk concentrations of 60 and 40 at% Cu at 300 K. The ratio $\text{Ni}{}^{\mathrm{+}}\text{Cu}{}^{\mathrm{+}}$ was nearly independent of CO pressure and temperature. The measured ratios of $\text{Cu}{}^{\mathrm{+}}{}_2\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$, $\text{Ni}{}^{\mathrm{+}}{}_2\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$ and $\text{CuNi}{}^{\mathrm{+}}\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$ with values about 10^?2 can be explained the basis of a statistical arrangement of Cu and Ni atoms in the alloy surface. The intensities of the MCO⁺ emissions are 10² times smaller than the corresponding values of the pure metals. No emission of M₂CO⁺ was found on CuNi during CO adsorption.     

Natural radiative lifetimes and hyperfine structure of the 4s26p2P32,12 levels of gallium

Natural radiative lifetimes and the signs of previously determined hyperfine coupling constants were determined for the $\text{4s}{}^2\text{6p}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext><mtext>,</mtext><mtext>1</mtext><mtext>2</mtext>}}$ levels of gallium. The lifetimes were found to be 167(4) and 172(9) ns, respectively. In addition, the quadrupole moments of ⁶⁹Ga [0.17(3) b] and ⁷¹Ga [0.10(2) b] were deduced, and the isotope shifts in the 639.7 and 641.3 nm Ga lines were determined.     

Energies and electromagnetic moments of deformed nuclei in the rare-earth region

Strutinsky-type cranking calculations with inclusion of pairing correlations have been performed for the rare-earth nuclei ^{156, 158, 164}Dy and ¹⁶⁴Er. The pairing effects contribute significantly and with their inclusion the calculated yrast spectra agree very well with experiments. Using Hartree-Fock-Bogouliubov cranking wave functions we have calculated the magnetic moments and quadrupole moments for states up to spin $\text{I = 20}\text{h}\text{?}$. The quadrupole moments are found to be constant over the whole spin range. The gyromagnetic factors g(I) show a strong I-dependence for ^{156, l58}Dy, a weaker one for ¹⁶⁴Er and none for ¹⁶⁴Dy. The sensitivity of this spin dependence on the single-particle occupation and the pairing degrees of freedom is studied. It is found that the spin variation of the gyrofactors is a rotational alignment effect.     

Hyperfine structure of 127I2 and 129I2 optical absorption lines

The hyperfine structure of ¹²⁷I₂ and ¹²⁹I₂ rovibronic absorption lines was investigated using either laser induced fluorescence of a collimated molecular beam or saturated absorption in a cell. From the measurements a value for the quadrupole moment ratio ${}^{129}\text{Q}{}^{127}\text{Q}\text{=}\text{0.699}$ is deduced, in good agreement with the result obtained from pure quadrupole spectra in the rf range.     

Study of the 45Sc(n, γ) reaction

Primary and secondary γ-rays from the ⁴⁵Sc(n, γ) reaction were measured at four resonances, two of them of p-wave (460.6 and 1060.4 eV) and the others of s-wave (3290 and 4330 eV) character. High accuracy measurements at near the thermal region (0.14-7.65 eV) resulted in an improved set of primary γ-ray energies and level energies above 1 MeV. We obtain a neutron binding energy $\text{B}{}_{\mathrm{<mtext>n</mtext>}}\text{(}{}^{45}\text{Sc}\text{) = 8760.5(2)}\text{keV}$. Absolute intensities of primary capture γ-rays were derived by comparison to the resonance capture in gold at 4.91 eV. El and Ml radiation strengths were observed to be about equal. No correlation of any kind [either between (n, γ) or (d, p) strengths or between adjacent s- and p-wave capture] was observed. The primary γ-ray spectrum following the capture of polarized neutrons in oriented and unoriented ⁴⁵Sc nuclei was studied. A combined χ² analysis of these two experiments resulted in 21 unique spin assignments and many spin restrictions. The fraction of spin J = 3^? in thermal capture was determined to be (92 + 5)%. From the observed transition rates to final states of known spin, J = 3 assignments result for the two p-wave resonances studied.     

Possible origin of S =12 ESR lines in alkali-TCNQ Salts

Solitons in spin Peierls systems are studied with emphasis on the contribution of solitions to the ESR spectra. It is pointed out that the ESR line ($\text{S =}\text{1}\text{2}$) observed in simple alkali-TCNQ salts can be due to solitons in spin Peierls state.     

Optically detected magnetic resonance of a relaxed excited state of atomic hydrogen centres in KCl and RbCl doped with I-

The ESR spectrum of relaxed excited state (RES) of inerstitial hydrogen centres in the “mixed” configuration with 3 Cl^- and 1 I^- ions next could be measured via the magnetic circular dichroism of the UV absorption bands. The g factor and I superhyperfine interactions of the RES and the ground state are practically the same, whereas the proton hyperfine interaction in the RES is reduced by ～ $\text{1}\text{3}$. The RES is a spin quartet charge transfer state with a very large zero field splitting.     

Integral rotation of 32− levels in 65Zn and 67Zn

Low-lying levels of ⁶⁵Zn and ⁶⁷Zn were excited by the Ni(α, n) reaction using enriched Ni and Ni₁₀Fe₉₀ targets. From the angular distributions of gamma rays, E2/M1 mixing ratios were obtained. In the iron alloy targets, integral spin precession was observed and used to measure the g-factors of two $\text{3}\text{2}{}^{\mathrm{?}}$ levels of ⁶⁵Zn. The results are discussed in terms of the shell and unified models of the odd Zn isotopes.     

Evidence from photoelectron spectroscopy for dissociative adsorption of oxygen on nickel oxide

XPS and UPS spectra from oxygen adsorption at high temperature on polycrystalline nickel oxide surfaces pre-heated at 700°C and 1450°C are presented. Adsorption results in complete loss of surface charge on both surfaces. There is an increase in intensity of the 0(1s) 529.7 eV peak, attributed to O^2? ions, and the $\text{Ni}\text{(2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}$ spectra show a shift of intensity to the 854.6 eV peak due to Ni²⁺ ions. The results are compared with previous data from kinetic, conductivity and electrochemical measurements. Agreement with a model of O^2? and nickel vacancy production is demonstrated. UPS spectra indicate considerable reorganisation of electronic charge in the surface of the 1450°C pre-heated oxide, after oxygen adsorption, giving an almost stoichiometric surface similar to that of a cleaved single crystal.     

Nuclear orientation of 109Cd and 115mCd in Cd

The quadrupole interaction frequencies of ¹⁰⁹Cd$\text{Cd}$ and ^115mCd$\text{Cd}$ have been measured by low-temperature nuclear orientation as +110(4) MHz and -102(12) MHz, respectively. The electric field gradient of Cd$\text{Cd}$ and the quadrupole moment of the $\text{5}\text{2}$⁺ 245 keV level of ¹¹¹Cd are deduced.     

A perturbed angular distribution in 70Ga

A pulsed proton beam and coaxial Ge(Li) detector were used to study the time dependence of the angular distribution of γ-rays resulting from the decay of the 879 keV state in ⁷⁰Ga, as excited by the ⁷⁰Zn(p, n)⁷⁰Ga reaction. A strong time-dependent attenuation of anisotropy was observed. The unperturbed value of the angular distribution is consistent with the assignment of spin I = 4 to the 879 keV level. The half-life of the 879 keV state was measured to be $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 22.7 ± 0.5}\text{ns}$.     

Magnetic field dependent optical dephasing in LaF3:Er3+

Optical dephasing of the 5388 Å transition between the lowest Kramers doublets of the ⁴S_{$\text{3}\text{2}$} and ⁴I_{$\text{15}\text{2}$} multiplets of Er³⁺:LaF₃ has been studied by photon echo, optical phase switching and optical free induction decay. Er³⁺?¹⁹F hyperfine interactions produce dephasing which is two orders of magnitude faster than in previously studied non-Kramers systems, but at high field changes in the spin dynamics result in microsecond dephasing. For the lower Zeeman component of ⁴S_{$\text{3}\text{2}$}, T₂ (=6μs) is independent of H₀ whereas for the upper component the dephasing is rapid and strongly field dependent. This is quantitatively accounted for by spin lattice relaxation of the upper component of ⁴S_{$\text{3}\text{2}$}. Below 20 kG concentration and temperature dependent dephasing due to electron spin diffusion is observed.     

A test of iso-scalar quadrupole renormalization in the 32− → 12−(Ex = 0.478 MeV) transition in 7Li

Electromagnetic studies have established that the $\text{3}\text{2}{}^{\mathrm{?}}\text{,}\text{1}\text{2}{}^{\mathrm{?}}$ ground state doublet in ⁷Li is well described by the LS coupling shell model, provided quadrupole effective charge is introduced. The results of microscopic calculations for the excitation of the $\text{1}\text{2}{}^{\mathrm{?}}$ level in inelastic proton scattering shown within indicate that an equivalent renormalization of the ⁷Li quadrupole neutron transition densities is also necessary. This verifies the assumption which was made in a previous calculation of the cross section for the excitation of the $\text{3}\text{2}{}^{\mathrm{?}}$ level in the ⁷Li+²⁴Mg reaction.     

Absorption spectra of Ni2+ in (NH4)2Mg(SO4)2·6H2O and Co2+ in Na2Zn(SO4)2·4H2O

Optical absorption spectra of Ni²⁺ in (NH₄)₂Mg(SO₄)₂·6H₂O and Co²⁺ in Na₂Zn(SO₄)₂·4H₂O single crystals have been studied at room and liquid nitrogen temperatures. From the nature and position of the observed bands, a successful interpretation could be made assuming octahedral symmetry for both the ions in the crystals. The splitting observed for ${}^3\text{T}{}_{\mathrm{1g}}\text{(F)}$ band in Ni²⁺ and ${}^4\text{T}{}_{\mathrm{2g}}\text{(F)}$ band in Co²⁺ at liquid nitrogen temperature have been explained as due to spin-orbit interaction. The extra band observed at 16,325 cm^-1 in the case of Ni²⁺ at low temperature has been interpreted to be the superposition of vibrational mode of SO^2-₄ radical on ${}^3\text{T}{}_{\mathrm{1g}}\text{(F)}$ band. The observed band positions in both the crystals have been fitted with four parameters B, C, Dq and ζ.     

An equation of state of the Ising systems

In the framework of the spin operators diagram technique the method of taking into account the correlation effects in magnetic system based on the idea of $\text{1}\text{z}$ expansion (z is the number of the nearest neighbours) is proposed. An equation of state of 3-dimensional Ising systems with the arbitrary spin values S in the first order in $\text{1}\text{z}$ is presented which considerably improves the mean field theory (being the zeroth order approximation). For various lattices the calculated values of Tc coinside within 1% with the results of the high-temperature expansions.